Centrifugal fuze unlatched by setback



Feb. 1, 1955 P. H. THOMPSON CENTRIFUGAL FUZE UNLATCHED BY SETBACK 2Sheets-Sheet 1 Filed Aug. 29, 1945 .1% m/ JM; mm mw S m. w

\ .l.., llllllllllllllllllllll im Feb. 1, 1955 P. H. THOMPSONCENTRIFUGAL FuzE UNLATCHED BY SETBACK 2 Sheets-Sheet 2 Filed Aug. 29,1945 Ruh@ m ummm, R mw m United States ate CENTRIFUGAL FUZE UNLATCHED BYSETBACK Parke H. Thompson, Kirkwood, Mo., assiguor, by mesneassignments, to Marion L. J. Lambert, doing business as Crystal-EloProducts Company, St. Louis, Mo.

Application August 29, 1945, Serial No. 613,299

9 Claims. (Cl. 102-80) This invention relates to fuzes, and with regardto certain more specific features, to safety fuzes for projectiles andthe like.

The present invention is an improvement upon the invention disclosed inmy United States patent applications Serial No. 537,563, filed May 27,1944, for Fuze, eventuated as Patent No. 2,495,431 and Serial No.592,131, led May 5, 1945, for Fuze, eventuated as Patent No. 2,564,797.

Among the several objects of the invention may be noted the provision ofa fuze which is armed in response to combined set-back and centrifugalaction; the provision of a fuze of the class described which willreliably arm at low angular velocity without making it unsafe inresponse to handling before loading, thus making it useful for artilleryproducing low angular projectile velocities, such as mortars, howitzersand the like; the provision of a fuze of this class which obtains asensitive release with a high degree of safety by employing a relativelyhigh ratio of spring rate to centrifugally deflected mass; and theprovision of a fuze of this class, the manufacturing constants of whichare easy to maintain, consistent with a high degree of accuracytandreliability in performance. Other objects will be in part obvious and inpart pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofthe application of which will be indicated in the following claims.

ln the accompanying drawings, in which one of various possibleembodiments of the invention is illustrated,

Fig. l is a longitudinal section of an exemplary projectile to which thefuze may be applied;

Fig. 2 is an enlarged longitudinal section of the nose of saidprojectile showing details of the invention, the parts being shown inunarmed safety position;

Fig. 3 is a cross section taken on line 3-3 of Fig. 2;

Fig. 4 is a detail side elevation of a ball rotor gyroscopic element ofFig. 2;

Fig. 5 is a left side View of Fig. 4;

Fig. 6 is a view similar to Fig. 2 but showing the parts in spinningarmed condition;

Fig. 7 is a cross section taken on line 7-7 of Fig. 6; and,

Fig. 8 is a plan view of the fuze in unarmed condition and removed fromthe ammunition, the view being observed on line 8 8 of Fig. 2.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

In prior centrifugally initiated fuzes a high rate of spin of theammunition was depended upon for arming. This was for the purpose ofexcluding chance movements from arming the ammunition prior to loadingfor firing. For the purpose, a relatively low ratio of spring rate tocentrifugally actuated mass was employed. This required rather criticalmanufacturing control in order to maintain accuracy. It also reduced theusefulness of said fuzes for mortars, howitzers, etc. which producerelatively low angular velocities of their projectiles. As will be seenhereinafter, the stated ends are obtained by the use of a novel set-backand centrifugally initiated fuze.

Referring now more particularly to Fig. 1, there is shown, by way ofexample, at numeral 1 a projectile which is exemplary of various typesto which the invention may be applied. This happens to be a piece ofbasedetonated ammunition but it is to be understood that the inventionis also applicable to point-detonated ammunition. ln any event the fuzeis preferably, though not necessarily, nose-initiated.

In particular, the projectile 1 consists in a shell 3 carrying at itsbase a booster charge 5. This charge 5 is at the rear end of a tube 7.rlhe tube 7, together with a conical member 9 and the shell 3, definesthe space for the explosive charge 11. The cone 9 so shapes the front ofthe charge 11 that a forwardly directed Munroe effect is obtained uponexplosion of the charge. On the front of the shell 3 is a tapered nose13. Upon the front end of this is screwed a pilot head 15 which carriesthe fuze per se, the latter being indicated generally at numeral 17 andshown separately in Fig. 8. When the fuze is set off, it directsexplosive energy through the cone 9 and tube 7 to the base-detonatingbooster 5, which in turn sets off the charge 11, the latter firingforward by reason of its Munroe effect. It is to be understood that ifthe invention were to be applied to a point-detonating booster chargethe booster 5, instead of being at the base of the shell, would be builtinto the tapered nose just behind the fuze. These alternatives referonly to the surroundings of the invention, which per se are in the fuzeor initiator 17.

Fastened into the inside rear of the head 15 is an internally threadedcup 19 in which is an opening 21. Centered within this cup is a holder23, a forward extension 25 of which passes through the opening 21. lnthe extension 25 is a primer charge 27. The rear end of this holder 23constitutes a spherical seat 29. It has a centering ange 31 which isheld in place by the threaded front end of a tubular body 33 threadedinto the cup. As will appear, body 33 serves as a catch. The tubularbody 33 is stepped as shown at 35 and 36 and in the region of thesesteps is provided with two oppositely located slits 37 (see Figs. 2, 3,6 and 8 particularly).

The rear portion of the tubular member 33 is flanged as shown at 39 forsupporting at the rear end a main initiator charge 41. The latter ishollow tapered at the rear, as shown at 43, for providing a rearwardlydirected Munroe effect toward the tube 7 and cone 9 (Fig. l). At itsforward end the initiator charge 41 is held in position by a ring 45threaded into the enlargement formed at the smallest step 35. This ring45 also holds in place an auxiliary pellet 47 which sets off theinitiator charge 41, this pellet being in the nature of a booster forthe initiator charge. The forward end of the ring 45 is made in the formof a spherical seat 49. This seat is in the rear of the enlargedcylindric chamber formed by the` larger step 36. At the front end ofthis enlargement is held said spherical seat 29. The enlarged cylindricchamber is indexed 51. In it is carried a spherical ball rotor orgyroscopic element 53. This rotor, unless locked (unarmed), is free torotate within the seats 49 and 29. Under released (arming) conditions itmay move from the unarmed position shown in Figs. 2 and 8 to the armedlposition shown in Fig. 6. This movement, when unlocked, is brought aboutgyroscopically under the spin of the shell 1, for reasons which willappear. The rotor has a diametral opening 55 flanged at its ends asshown at 57. Between the flanges 57 and in the opening 55 is carried adetonator charge 59. For the reasons given in the above-mentionedpatents and in United States Patent 2,155,100, a ball rotor gyroscopicelement of this type, under spinning action of the projectile on itslongitudinal axis L-L, will tend to preeess the gyroscopic axis G-G ofthe ball rotor into position parallel with said axis of spin L L. Thus,when unlocked the gyroscopic ball rotor will move from the positionshown in Figs. 2 and 8 to that shown in Fig. 6, moving anticlockwise(Fig. 8) in the process. The problem, however, is to prevent suchmovement to an arming position prior to firing the projectile.

In order to lock the ball rotor into the position shown in Figs. 2 and8, it is provided on opposite sides with notches or grooves 61. Thesehave sloping sides to make them V-shaped, as indicated, and areparallel. They are angled with respect to the gyroscopic axis G-Gthrough the hole 55 (see Figs. 4 and 5). In the unarmed position of therotor (Fig. 2) the notches are parallel with the axis of spin of theprojectile. This places the hole 55 and axis G-G at an angle asindicated in Figs. 2, 4 and 8 wherein, even if the primer 27accidentally explodes, the detonator 59 will not, since the latter isout of ex plosive communication with the primer tube 23. The detonatoronly comes into explosive communication with the primer after it hasbeen rotated from the Fig. 2 (or 8) to the Fig. 6 position. To preventsuch rotation before firing, I provide at the rear of the tubular body33 a semicircular and grooved detent sleeve 62 which is welded intoposition on the surface of the body 33. The edges 63 of this sleeve 62lie substantially in a plane including sides of the slots 37 (see Fig.8). The sleeve 62 is also formed with two spaced grooves 65 and 67 whichare joined by a part 69 of smaller diameter. This part 69, however, isspaced from the tube 33 to provide a semicircular passageway.

At numeral 71 is shown a generally hairpin-shaped spring wire which hastwo normally parallel cantilever spring legs 73 lying on the surface ofthe tube 33 and in a plane passing through its axis. The normally freeend portions of these cantilever legs 73 may thus be made to lie in theslots 37 (Fig. 8). Their tips 75, as shown in Figs. 2 and 8 may be madeto lie beyond the forward ends of said slots 37 under conditions whichwill appear. Under such conditions, if the grooves 61 of the ball rotor53 are made to lie under the slots 37. then the spring legs 73 will alsolie in said grooves 61 and hold the gyroscopic ball rotor in unarmedposition as shown in Figs. 2 and 8.

In order to hold the safety spring wire 71 in said safe position ofFigs. 2 and 8, the rear end is formed with a half loop 77 which reachesaround the tube 33 and is located in the foremost grooves 65 of thesemicircular sleeve 62. The shape of the loop 77, as indicated in Fig.3, is such that there is a detent vholding action of the loop in thegroove 65. However` under high enough axial or linear acceleration, aswhen the projectile is tired, the entire safety spring wire 7l may movebackward from the Fig. 2 position. This will occur with a snap action,since the semicircular loop 77 is resilient and will pass from theforemost groove 65, under part 69 and into the rearmost groove 67. Itwill end up its relatively rearward travel by snapping into the groove67 with a second detent action.

When the safety spring wire 71 is forward with its loop 77 in groove 65,its tips 75 are locked against any substantial outward travel, evenunder high-speed spin of the projectile. These tip portions cannot leavethe grooves 61 in the ball rotor 53 and hence the latter is safelylocked in its unarmed position of Figs. 2 and 8. The legs 73 are eachsupported at both ends like simple beams and wire 71 may then bereferred to as a positive latch. However, after the spring 71 has movedback to the position shown in Fig. 6, any rotation of the projectile onits longitudinal axis L-L (due to firing) will cause the now unlockedlegs 73 to become spring cantilevers which spring out from the grooves37 as shown in Fig. 6. This releases the gvroscopic ball rotor 53 sothat it may function dynamically to move from the Fig. 2 to the Fig. 6position. This places the fuze in its armed (Fig. 6) position.

Complete operation is as follows:

Starting with the device in its safe, unarmed position such as shown inFig. 2, it may be assumed that the projectile 1 is loaded into asuitable tiring mechanism such as a gun, rocket launcher or the like. Itis presumed that either the gun or the proiectile, or both. incorporatemeans whereby the projectile is spun during ight. Upon firing, set-backforces due to linear acceleration along axis L-L immediately cause thespring latch means 17 relatively to move backward so that the loop 77moves with snap action from groove 65 to groove 67. This is due to theinertia of member 17. These forces also hold the rotor 53 tightlyagainst the seat 49. Thus the latch members 75 move from the catch 33.

At, about or soon after the time that the initial linear accelerationtakes place, the angular acceleration sets in which causes theprojectile to rotate on its longitudinal axis. thus also causing thespring latch 71 to be rotated, as Well as the gyroscopic ball rotor 53.The spring latch 71 cannot lag in its rotation on the tube 33, since theedges 63 of the semicircular sleeve 62 drive the legs 73 (Fig. 7). Slots37 also have a driving action on legs 73. Thus at a predeterminedangular velocity, the legs 73 deect out through the grooves 37 to theirreleasing positions shown in Fig. 6. At this time they function asspring cantilevers. After the projectile has cleared the barrel, or whenso-called creep or set-forward forces set in, the then spinning ballrotor 53 precesses gyroscopically from its angular position of Fig. 2 tothe coaxial position (Fig. 6). This arms the fuze so that when the head15 strikes an object and collapses upon the primer 27 the latter underimpact will tire into the detonator 59. Thereafter a train of explosionsis set off through the materials 47, 41, 5 and 11 to explode theprojectile.

From the above it will be seen that the device is quite simple. Theparts are easy to manufacture in quantity. Extreme accuracy is notnecessary for consistent and safe operation. The long spring legs 73inherently have a very high spring rate with respect to their own masseswhich, through centrifugal action, deect them. Thus at relatively lowangular projectile velocities the masses of the legs 73 cause largedetiections of the same as indicated in Fig. 6. This is what is meantabove by the device having a relatively large ratio of spring rate tocentrifugally operating mass. With such a construction a quick anddefinite release of the ball rotor is obtained at low angular velocity.without sacrificing safety before such values are reached. For example,one form of the present device will arm reliably between 1500 and 2000R. PA M. of the projectile.

While l have shown the primer 27 as being in the extension 23, it is tobe understood that instead of this primer l may employ in this extensiona tiring pin which upon impact may be pushed back into the armed rotoralong the lines described in said application. In such a case the primerto be struck by the tiring pin would be loaded into the rotor along withthe detonator shown. Such construction would be an operating equivalent,so far as the impact operation is concerned. and some of the appendedclaims are intended generically to cover such a construction.

Tt will be seen that when the latch spring 71 is forward as indicated inFig. 2, its legs 73 act as beams supported at both ends, namely in thegroove 65 and within the chamber containing the rotor. As such, theselegs 73 positively lock the rotor against movement from its unarmed toits armed position. On the other hand, after set-back, when the loop 77is in the groove 67, then the spring legs 73 are converted into springcantilever beams supported only at the end near the loop 77. As suchthese legs 73 are loaded as cantilever springs or beams undercentrifugal force and therefore may move out to the position shown inFig. 6 under rotation of the pro- 'ecti e. l It should be observed thatthe sides of the notches 61 in the ball rotor 53 have sloping sides.Such sides are preferable to parallel or undercut sides since either ofthe latter would tend to effect a locking action between the rotor andthe legs 73 under tendency of the rotor to move from unarmed to armedposition. With the sloping sides on the notches 61 they tend to cam outthe legs 73 without binding. This action is especially desirable wherehigher cantilever spring rates are used.

It should be understood that` although the ball 53 is shown as being ofsubstantially spherical form. other euuivalent forms may be used for thepurpose of bringing it from its unarmed position of Fig. 2 to the armedposition of Fig. 6 under spin of the projectile which carries it. So faras the present invention is concerned, the primary criterion for theball 53 is that it shall carry and position a detonator or similarcharge so that the charge is safe under unarmed conditions and exposedfor detonation under armed conditions. To this end the ball in effectconstitutes a gyroscopic element having the axis G-G around which is themaximum moment of inertia, which axis under unarmed conditions is at anangle to the axis of the projectile and parallel thereto when armedunder spin conditions. Therefore in the appended claims the ball rotor53 or its equivalent will therefore be referred to broadly as agyroscopic rotor element.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

1 claim:

1. A fuze for projectiles comprising a gyroscopic rotor adapted underspin of the projectile to precess from an unarmed to an armed position,a tubular holder for the rotor, a two-legged hairpin type spring latchhaving a semicircular connecting part slidable on the holder in responseto set-back forces, said rotor being oppositely notched and said holderhaving openings adapted to expose the notches to cooperation with thelegs of the latch in an initial position of the latch, means for lockingthe legs of said latch against movement under centrifugal force in itsinitial position when it is latched with the rotor, the legs of thelatch retracting from said lastnamed means when the latch is set backthereby to release the legs of the latch so that under centrifugal forcethey may spring out through said holder openings away from latchingpositions in said notches.

2. A fuze for projectiles comprising a gyroscopic rotor adapted underspin of the projectile to precess from an unarmed to an armed position,a tubular holder for the rotor, a two-legged hairpin type spring latchhaving a semicircular connecting part slidable on the holder in responseto set-back forces, said rotor being oppositely notched and said holderhaving openings adapted to expose the notches to cooperation with thelegs of the latch in an initial position of the latch, means for lockingthe legs of said latch against movement under centrifugal force in itsinitial position when it is latched with the rotor, the legs of thelatch retracting from said last-named means when the latch is set backthereby to release the legs of the latch so that under centrifugal forcethey may spring out through said holder openings away from latchingpositions in said notches, and a detent means on the tubular holdercooperating with said connecting part of the latch resiliently to holdit in latching position.

3. A fuze for projectiles comprising a gyroscopic rotor movable underspin of the projectile from an unarmed to an armed position, a supportfor said rotor providing a holding means on the support and providing aguide, said rotor having notch means and said support having openingswith which said notch means align when the rotor is in unarmed position,a spring latch comprising a pair of oppositely located spring legsmovable radially through said openings, the ends of said legs beingmovable axially into said holding means to be locked positively againstmovement from the openings under centrifugal force, means connectingsaid spring legs and sliding on said guide, detent means on said guideand engageable by said connecting means for normally holding the latchagainst axial movement whereby it is locked in said second holding meansagainst centrifugal force but permitting movement of the latch underset-back forces to a second position wherein the legs of the latch aremovable from said holding means to a position in which they may moveunder centrifugal force out through said openg4. A fuze for projectilescomprising a gyroscopic rotor movable under spin of the projectile froman unarmed to an armed position, a support for said rotor providing aholding compartment for the rotor, and providing a cylindric extensiontherefrom, said rotor having opposite notch means and said supporthaving openings with which said notch means align when the rotor is inunarmed position, a spring latch comprising a pair of oppositely locatedspring legs movable laterally through said openings, the ends of saidlegs being movable axially into said compartment and into a position tobe locked positively against movement from the slots under centrifugalforce, a spring loop joining said spring legs and at least partiallysurrounding said extension, detent means on said extension engaged bysaid loop for normally holding the latch against axial movement andwherein it is locked against centrifugal force but permitting movementof the latch under set-back forces to a second position wherein the legsof the latch are movable from said chamber to a position in which theymay under centrifugal force move out through said openings.

5. A fuze for projectiles comprising a gyroscopic ball rotor having adiametral opening containing a detonator and movable under projectilespin from a position in which the detonator is in an unarmed position toa position in which the detonator is in its armed position, parallelnotches on opposite sides of said rotor and at an angle s to the axis ofthe opening in which the detonator is located, a holder forming arelatively large diameter chamber within which are forwardly andrearwardly located seats for the rotor, said detonator aligning withsaid seats when in armed position, impact-initiated means associatedwith the front seat for exploding the detonator when the latter is inarmed position, said holder forming a sleeve behind the rearmost seat ofdiameter smaller than that of said chamber, said holder having oppositeslots providing openings into the chamber with which said rotor groovesmay align when the rotor is in unarmed position, a spring latchcomprising cantilever spring arms lying parallel to and movable radiallyinto and out of said slots and said grooves and when in the groovesbeing movable axially into said chamber to be locked against movement bycentrifugal force, and a semicircular loop joining said spring legs andslidable on said sleeve.

6. A fuze for projectiles comprising a gyroscopic ball rotor having adiametral opening containing a detonator and movable under projectilespin from a position in which the detonator is in an unarmed position toa position in which the detonator is in its armed position, parallelnotches on opposite sides of said rotor and at an angle to the axis ofthe opening in which the detonator is located, a holder forming arelatively large diameter chamber within which are forwardly andrearwardly located seats for the rotor, said detonator aligning withsaid seats when in armed position, impact-initiated means associatedwith the front seat for exploding the detonator when the latter is inarmed position, said holder forming a sleeve behind the rearmost seat ofdiameter smaller than that of said chamber, said holder having oppositeslots providing openings into the chamber with which said rotor groovesmay align when the rotor is in unarmed position, a spring latchcomprising cantilever spring arms lying parallel to and movable radiallyinto and out of tsaid slots and said grooves and when in the groovesbeing'movable axially into said chamber to be locked against movement bycentrifugal force, and a semicircular loop joining said spring legs andslidable on said sleeve, a semicircular detent cylinder having spaceddetent grooves, said detent cylinder being attached to said sleeve, theedges of the detent cylinder lying next to said spring legs and saidloop having a detent engagement with either of said grooves whereby whenthe loop is in the forward detent groove said latch arms are locked insaid rotor compartment against action by centrifugal force and beinglocked in said rotor grooves to hold the latter positively in unarmedposition, and whereby linear acceleration of the projectile will setback the spring latch to place said loop in the second groove andreleasing the spring legs so that under centrifugal force they may movefrom the rotor groove through said slot to free the rotor for gyroscopicprecession to armed position.

fuze for projectiles comprising a gyroscopic safety rotor movable underspin of the projectile from an unarmed to an armed position, a supportfor the rotor, a latch beam slidable near one end on the holder, saidrotor having notch means engageable by the latch beam when the rotor isin unarmed position, holding means on the support for receiving theother end of the latch beam in one position wherein it engages saidnotch to hold the rotor in safe position, detent means associated'withthe first-mentioned end of the beam adapted resiliently to hold it, saidbeam being movable under set-back forces out of the detent into aposition where its second-mentioned end is released from the holdingmeans on the support, said beam being thus converted from one supportedat both ends to one supported only at one end whereby the other end maybe moved centrifugally out of said notch under spin of the projectile.

8. A fuze for projectiles comprising a gyroscopic safety rotor movableunder spin of the projectile from an unarmed to an armed position, asupport for the rotor, a spring latch beam lslidable near a irst end ofthe beam on the holder, said rotor having notch means engageable by thespring latch beam when the rotor is in unarmed position to hold therotor safe, means associated with the support for receiving a second endof the spring latch beam in one position wherein it engages said notch,detent means associated with the first end of the spring latch beamadapted resiliently to hold it, said beam being movable under set-backforces out of the detent into a position where its second end isreleased from the holding means on the holder, whereby said spring beamis converted from one supported at both ends to one supported only atone end to function as a cantilever spring adapted to be movedcentrifugally out of said notch under spin of the projectile.

9. A fuze for a projectile comprising a gyroscopic rotor adapted underprojectile spin to precess from an unarmed to an armed position, a latchmounted for substantially axial movement from an initial position to aset-back position in response to set-back forces, said latch includingan axially extending spring cantilever having a free end biasedsubstantially radially toward engagement with the rotor to preventprecession of the rotor but movable against bias by centrifugal force, acatch engageable with said free end in its initial position to preventradial movement of the free end in response to spin of the projectilebefore set-back forces occur, the latch being disengaged ReferencesCited in the le of this patent UNITED STATES PATENTS 2,014,393 MathsenSept. 17, 1935 2,335,842 Nichols Nov. 30, 1943 FOREIGN PATENTS 156,556Great Britain Apr. 7, 1921

